Many pathogenic bacteria utilize unique nano-reactors called bacterial microcompartments to metabolize diverse nutritional sources. This helps pathogenic organisms thrive in human tissues. The bacterial microcompartment is a specialized organelle composed of enzymes surrounded by a protein shell. To function, compounds to be broken down within the bacterial microcompartment must cross the shell, and likewise the breakdown products must be released. The goal of the proposed research is to study the structural basis of function of these shells, to obtain a snapshot at atomic resolution o the structure of a shell and to deduce the blueprint for its assembly. We will also identify what structural features of the shell determine its permeability properties. The results of this study wll enable the design of therapeutics to disrupt bacterial microcompartment assembly and function. They could likewise be used to design useful bacterial microcompartments for applications in biomedicine.